Acute normovolemic hemodilution in cardiac surgery: rationale and design of a multicenter randomized trial

Background: Minimizing the use of blood component can reduce known and unknown blood transfusion risks, preserve blood bank resources, and decrease healthcare costs. Red Blood Cell (RBC) transfusion is common after cardiac surgery and associated with adverse perioperative outcomes, including mortality. Acute normovolemic hemodilution (ANH) may reduce bleeding and the need for blood product transfusion after cardiac surgery. However, its blood-saving effect and impact on major outcomes remain uncertain. Methods: This is a single-blinded, multinational, pragmatic, randomized controlled trial with a 1:1 allocation ratio conducted in Tertiary and University hospitals. The study is designed to enroll patients scheduled for elective cardiac surgery with planned cardiopulmonary bypass (CPB). Patients are randomized to receive ANH before CPB or the best available treatment without ANH. We identified an ANH volume of at least 650 ml as the critical threshold for clinically relevant benefits. Larger ANH volumes, however, are allowed and tailored to the patient's characteristics and clinical conditions. Results: The primary outcome is the percentage of patients receiving RBCs transfusion from randomization until hospital discharge, which we hypothesize will be reduced from 35% to 28% with ANH. Secondary outcomes are all-cause 30-day mortality, acute kidney injury, bleeding complications, and ischemic complications. Conclusion: The trial is designed to determine whether ANH can safely reduce RBC transfusion after elective cardiac surgery with CPB. Study registration: This trial was registered on ClinicalTrials.gov in April 2019 with the trial identification number NCT03913481.